#include <stdio.h>
#include <math.h>

#define Epsilon 1.0E-6

int main()
{
    float num,pre,this;
    do
    {
        scanf("%f",&num);
    }while(num<0);
    if(num==0)
    printf("the root is 0");
    else 
    {
        this =1;
        do
        {
            pre=this;
            this=(pre+num/pre)/2;
        }while(fabs(pre-this)>Epsilon);
    }
    printf("the root is %f\n",this);
}